The present invention is directed to methods and apparatus for adaptively selecting a communications mode in high frequency systems (e.g., 60 GHz), and more particularly to selecting a high frequency communications mode based on characteristics of a communications channel.
High data rate (e.g., about 2.5 Gbit/s) wireless communications systems are increasingly desirable with the greater use of wireless devices. High frequency data rate wireless communications systems, such as 60 GHz systems, provide wider communications bandwidth (e.g., about 2 GHz) and thereby increase the amount of data that may be transmitted/received between devices. Compared to lower frequency systems, signals in high frequency systems (e.g., 60 GHz carrier frequency systems) are prone to greater atmospheric attenuation (e.g., delay dispersion or delay spread), making them difficult to operate over long distances (e.g., greater than 10 meters).
For example, high frequency signals in the 57-64 GHz frequency range may be subject to resonance of oxygen molecules and may thereby be severely attenuated. Even over relatively short distances (e.g., less than 10 meters), rain fade may pose a serious problem, caused when absorption by rain reduces signal strength. In climates other than deserts, absorption due to humidity may also have an impact on propagation. Thus, the transmitters and receivers operating in high frequency systems have to be designed specifically to compensate for the signal attenuation factors that are present in high frequency systems. In particular, the power amplifier (PA) efficiency at the transmitter and the analog-to-digital converter (ADC) bit-width at the receiver may have operate under more constraints than traditional lower frequency systems. For example, a power amplifier may be required to operate linearly over a wider interval or the speed or precision of an ADC may be to be increased.
The high frequency communications mode circuitry that is used to generate signals that compensate for attenuation and other channel characteristics (e.g., delay spread) in short range high frequency communications may be less complex and may consume less power than the high frequency communication mode circuitry that is used to generate signals that compensate for the attenuation factors in long range high frequency communications. This is typically because the peak-to-average-ratio (PAPR) in the short range signal may be lower than that in the long range signal. Thus, a device having a particular high frequency communications mode implementation may be suitable for use in one type of application (e.g., short range) but not in another (e.g., long range). As defined herein, the terms delay dispersion and delay spread mean the time difference between the arrival moment of a first multi-path component of the signal and the last multi-path component in systems where an identical signal arrives at its destination at different times.
Accordingly, it is desirable to provide enhanced systems and methods for adaptively selecting a high frequency communications mode implementation based on characteristics of a communications channel (e.g., attenuation factors present in the communications channel and delay spread).